1. Field of the Invention
The present invention relates to a device for detecting an operation condition of a clamp which fixes a work or the like.
2. Explanation of Related Art
The operation detecting device of this kind projects a detecting rod from one end of a clamp rod to an area outside one end wall of a housing. A limit switch senses a moving condition of the detecting rod (for example, Japanese Patent Public Disclosure No. 2001-87991).
A clamp is used, for example, to fix a work of a machine tool. Therefore, the foregoing conventional technique had a problem that lots of cutting lubricant which is dispersed when machining shortens a service lifetime of the limit switch. Further, it had another problem that a large installation space is required for the limit switch.
The present invention has an object to provide a highly reliable and compact device for detecting an operation condition of a clamp.
In order to accomplish the above object, the present invention has constructed an operation detecting device of a clamp in the following manner, for example, as shown in FIGS. 1 to 4 or in FIGS. 5 to 9C.
A clamp rod 5 is inserted into a housing 3 axially movably. The housing 3 has one end wall 3b formed with a detecting hole 58 substantially concentrically with an axis of the clamp rod 5. The detecting hole 58 has a peripheral surface opened to provide at least one inlet hole 71 (72) for supplying pressurized fluid. A detecting member 62 is axially movably fitted into the detecting hole 58. The detecting member 62 has an outer peripheral surface provided with a closing surface 68 which closes an opening portion 71a (72a) of the inlet hole 71 (72) and with a recess 69 which communicates the opening portion 71a (72a) with the outside air. The clamp rod 5 has one end portion provided with an actuation portion 5a. The actuation portion 5a is connected to the detecting member 62 so that it can make a relative movement radially.
The present invention offers the following function and advantages.
When detecting an operation of the clamp, pressurized fluid such as compressed air is supplied to the inlet hole. In the case where the opening portion of the inlet hole faces the recess of the detecting member, the pressurized fluid which has been supplied to the inlet hole is discharged to an exterior area through the recess to result in lowering a pressure of the pressurized fluid than a set pressure. On the other hand, in the event the inlet hole has the opening portion closed by the closing surface of the detecting member, the pressurized fluid is prevented from being discharged to result in retaining the set pressure.
In consequence, it is possible to detect which condition the detecting member is switched over to by detecting the pressure of the pressurized fluid. This makes it possible to detect the operation condition of the clamp rod.
As mentioned above, the operation detecting device of the present invention utilizes the pressurized fluid such as compressed air. Therefore, differently from the limit switch or the like of the above-mentioned conventional technique, it is inhibited from deteriorating due to cutting lubricant or the like to result in having its service lifetime extended and its reliability enhanced. In addition, the operation detecting device can be provided in one end wall of the housing and therefore can be made compact.
Further, the present invention connects the actuation portion provided at one end portion of the clamp rod and the detecting member to each other so that they can make a relative movement radially. Accordingly, it offers the following advantages.
The above arrangement absorbs misalignment of the axis of the clamp rod with an axis of the detecting hole, thereby enabling the detecting member to be smoothly inserted into the detecting hole.
Moreover, in the case where a large bending moment has acted on the clamp rod at the time of clamp driving, there is a likelihood that the actuation portion provided on the clamp rod bends although only slightly. In this case, the bent actuation portion makes a relative movement radially with respect to the detecting member, thereby making it possible to prevent the detecting member from being pushed to the detecting hole. Thus the detecting member smoothly moves through the detecting hole to result in the possibility of detecting the operation of the clamp assuredly and precisely.
The present invention includes a device wherein the actuation portion 5a is connected to the detecting member 62 so that it can make a relative movement axially. In this case, since the bent actuation portion can be surely prevented from pushing the detecting member to the detecting hole, it is possible to detect the operation of the clamp more precisely.
The present invention further includes a device wherein the actuation portion 5a is connected to the detecting member 62 in such a state that the former is prevented from making a relative rotation around the axis. In this case, it is possible to retain the detecting member at substantially a constant posture. This can decrease an area occupied by the recess, of an area of the outer peripheral surface of the detecting member. Therefore, a guiding area of the detecting member with respect to the detecting hole increases to result in being able to smoothly move the detecting member.
The present invention still more includes the following device.
In this device, the detecting hole 58 has one end communicated with the outside air. The recess 69 of the detecting member 62 is defined by a groove extending axially. The recess 69 composed of the groove has one end opened to one end surface of the detecting member 62 and has the other end opened to the other end surface of the detecting member 62. According to this invention, it is possible to provide a detecting device which has a simple structure and a high reliability.